As is known, the filtration of diesel in the motoring sector is generally obtained with a group that comprises an external casing provided with a substantially beaker-shaped body, the open end of which is closed by a cover. At least one from between the cover and the beaker-shaped body is provided with an inlet for the diesel to be filtered and an outlet of the filtered diesel. A filter cartridge is contained internally of the casing, which filter cartridge is suitable for sub-dividing the internal volume of the casing into two distinct chambers, of which a first chamber is in communication with the inlet and a second chamber communicates with the outlet. In this way, the diesel flowing from the inlet towards the outlet of the filter group is forced to cross the filter cartridge, which retains the impurities that might be present therein.
A certain quantity of water is also present in the diesel, which due to the greater specific weight thereof with respect to the specific weight of the fuel to be treated (for example diesel oil) tends to accumulate on the bottom of the beaker body and must therefore be eliminated during the functioning of the filter group.
In the prior art, for facilitating the separation of the water from the fuel, filter walls are generally used which are able to separate the water by coalescence from the fuel and/or hydrophobic nets which keep the water separated from the fuel, so that the water collects by force of gravity on the bottom of the casing.
Further, also known is the use of discharge conduits associated to the casing of the filter group which place the lower part of the casing, where the water tends to collect, in communication with discharge means and/or aspirating means of the water, so that the accumulated water is constantly emptied from the casing.
To detect the presence of accumulated water in the casing, with the aim of preventing the level of water from exceeding a predetermined maximum level and so that it cannot therefore be accessed and sent into the combustion chamber, there are sensors present (known as water in fuel sensors) which are associated to the casing in such a way that a sensitive part of the sensor is located in proximity of the bottom thereof.
The sensors detecting the presence of water are operatively connected to the electronic board of the vehicle and are configured so as to generate an alarm signal in a case where the water reaches the maximum level, which generally corresponds to the level at which the sensitive part of the sensor is located internally of the casing.
When the alarm signal is generated it is sufficient to empty the water present on the bottom of the casing via the discharge conduit.
The water presence sensors in practice comprise an electric circuit that can terminate with one or more uncovered electrodes, which are the sensitive part of the sensor and are configured to be arranged internally of the casing and immersed in the fluid being filtered.
The level the water has reached in the casing is calculated from the measurement of the conductivity of the liquid about the electrodes, which is different if the electrodes are immersed in the diesel or in water.
There exist water presence sensors the electrodes of which are fixed to the bottom of the casing or which are fixed to the lower end of a longitudinal stem which branches from the upper cover of the casing.
A drawback encountered in the filter groups of known type, in which the water presence sensor is integrated in the casing, is the fact that a non-original filter cartridge or a cartridge arranged wrongly internally of the casing might obscure the sensor or render it ineffective.
Lastly, a drawback encountered in known filter groups relates to the fact that the water level sensor is located at an height independently of the filter cartridge, and might therefore be located at a greater height with respect to the level of the lower support plate of the filter cartridge and therefore at a level corresponding to a sector of the filter wall, which would therefore be wetted by the water that accumulates on the bottom.
An aim of the present invention is to obviate the above-mentioned drawbacks in the prior art, with a solution that is simple, rational and relatively inexpensive.
The above aims are attained by the characteristics of the invention reported in the independent claim. The dependent claims delineate preferred and/or particularly advantageous aspects of the invention.